// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/raster/synchronous_task_graph_runner.h"

#include <stdint.h>

#include <algorithm>
#include <utility>

#include "base/threading/simple_thread.h"
#include "base/threading/thread_restrictions.h"
#include "base/trace_event/trace_event.h"

namespace cc {

SynchronousTaskGraphRunner::SynchronousTaskGraphRunner() { }

SynchronousTaskGraphRunner::~SynchronousTaskGraphRunner()
{
    DCHECK(!work_queue_.HasReadyToRunTasks());
}

NamespaceToken SynchronousTaskGraphRunner::GenerateNamespaceToken()
{
    return work_queue_.GenerateNamespaceToken();
}

void SynchronousTaskGraphRunner::ScheduleTasks(NamespaceToken token,
    TaskGraph* graph)
{
    TRACE_EVENT2("cc", "SynchronousTaskGraphRunner::ScheduleTasks", "num_nodes",
        graph->nodes.size(), "num_edges", graph->edges.size());

    DCHECK(token.IsValid());
    DCHECK(!TaskGraphWorkQueue::DependencyMismatch(graph));

    work_queue_.ScheduleTasks(token, graph);
}

void SynchronousTaskGraphRunner::WaitForTasksToFinishRunning(
    NamespaceToken token)
{
    TRACE_EVENT0("cc", "SynchronousTaskGraphRunner::WaitForTasksToFinishRunning");

    DCHECK(token.IsValid());
    auto* task_namespace = work_queue_.GetNamespaceForToken(token);

    if (!task_namespace)
        return;

    while (!work_queue_.HasFinishedRunningTasksInNamespace(task_namespace)) {
        bool succeeded = RunTask();
        DCHECK(succeeded);
    }
}

void SynchronousTaskGraphRunner::CollectCompletedTasks(
    NamespaceToken token,
    Task::Vector* completed_tasks)
{
    TRACE_EVENT0("cc", "SynchronousTaskGraphRunner::CollectCompletedTasks");

    DCHECK(token.IsValid());
    work_queue_.CollectCompletedTasks(token, completed_tasks);
}

void SynchronousTaskGraphRunner::RunUntilIdle()
{
    while (RunTask()) {
    }
}

bool SynchronousTaskGraphRunner::RunTask()
{
    TRACE_EVENT0("toplevel", "SynchronousTaskGraphRunner::RunTask");

    // Find the first category with any tasks to run. This task graph runner
    // treats categories as an additional priority.
    const auto& ready_to_run_namespaces = work_queue_.ready_to_run_namespaces();
    auto found = std::find_if(
        ready_to_run_namespaces.cbegin(), ready_to_run_namespaces.cend(),
        [](const std::pair<const uint16_t,
            TaskGraphWorkQueue::TaskNamespace::Vector>& pair) {
            return !pair.second.empty();
        });

    if (found == ready_to_run_namespaces.cend()) {
        return false;
    }

    const uint16_t category = found->first;
    auto prioritized_task = work_queue_.GetNextTaskToRun(category);
    prioritized_task.task->RunOnWorkerThread();

    work_queue_.CompleteTask(std::move(prioritized_task));

    return true;
}

} // namespace cc
